1. Technical Field
Aspects of the present invention relate to a print data generating apparatus, an image processing apparatus, and print data generating programs and image processing programs therefor capable of creating print data which is used for printing in the printing apparatus, and more specifically, creating print data suitable for a printing operation using white ink in the printing apparatus.
2. Related Art
Conventionally, in an inkjet printing apparatus that performs recording by ejecting inks onto a recording medium, the inks are ejected from ejecting nozzles, which are provided at an end of ink channels, by leading the inks from ink reservoirs to a plurality of ejecting channels in inkjet heads, and by selectively activating actuators (e.g., heating elements, piezoelectric elements, and the like). When an image is formed in colors, each of pixels composing the image is resolved, for example, into the three primary colors, which are cyan (C), magenta (M), and yellow (Y), then a colored pixel is formed as the inks adjusted in their densities are ejected onto the recording medium. Also, a pixel which contains black as a component is generally reproduced as a black (K) ink is ejected onto the recording medium.
In recent years, a white ink as well as CMYK inks (hereinafter referred to as “colored inks”) has been used so that, for example, a high-quality image in better reproducibility without being bounded by factors of the recording medium such as a color and brightness of the recording medium. Such a use of the white ink is disclosed in Japanese Patent Provisional Publications Nos. HEI7-114241, 2002-38063, 2005-262553, HEI7-110568, 2001-253065, 2002-46303, and 2004-25603 (hereinafter referred to as '241 publication, '063 publication, '553 publication, '568 publication, '065 publication, '303 publication, and '603 publication respectively). According to these techniques, images in higher quality can be achieved by covering a base color of the recording medium with the white ink, and reproducing light colors by adding the white ink to colored inks.
However, according to '241 and '063 publications, printing in the white ink is executed on an entire area or an entire record objective area of the recording medium. Therefore, there has been a problem that an amount of the white ink to be used is increased, therefore it is inefficient for printing speed and print cost.
Further, according to '063, '568, '065, and '303 publications, printing is binary-controlled, and the image is formed based on the control as to whether the white ink is ejected or not on every pixel. However, ejecting the white ink under the binary control cannot reproduce white scales (i.e., gradation) on the recording medium. Therefore, there has been a problem that a pseudo-outline is generated on a border between an area printed in the white ink and an unprinted area, and the image quality is deteriorated. Additionally, when the white ink is ejected onto each pixel, the white ink is ejected uniformly regardless of closeness of the color of the pixels to the base color of the recording medium, thus, the amount of white ink to be used is yet increased.
Furthermore, in the printing apparatuses according to '063, '553, and '065 publications, as to whether the white ink is ejected on each pixel and/or an amount of the white ink to be ejected is determined based on factors such as a color and transparency of the recording medium. However, it is difficult to make an accurate estimate of a color and brightness of each pixel in actual printing of the image by only judging the color and the transparency of the recording medium. Therefore, in order to print a high-quality image using the white ink, a supplier of the printing apparatuses including a manufacturer and a designer has been required to actually execute sample printing on the recording medium and determine a preferable ejecting rate of the white ink (i.e., a white ink level) with respect to each pixel, based on human eye observation.
Furthermore, according to the technique disclosed in '603 publication, an amount of the white ink to be ejected is increased as input levels of the colored inks (CMY) decrease. In this method, if the input levels of the colored inks are high, the amount of the white ink to be ejected decreases, therefore, if the base color of the recording medium is strong, the image quality of printing in the colored inks is deteriorated by the lack of the white ink and the base color of the recording medium affecting the image printed in the colored inks. Thus, similarly to above, it has been difficult to estimate accurately how the color and/or brightness of each pixel in the image as a print output solely by considering the input levels of the colored inks.